Many audio speaker systems include multiple speaker drivers that are each responsible for producing sounds in specific frequency ranges. For example, conventional speaker systems often include one or more woofers having a speaker driver designed to produce low-frequency sounds (i.e., approximately 20 Hz-250 Hz), one or more midrange drivers designed to produce midrange sounds (i.e., approximately 250 Hz-2 kHz), and one or more tweeters having speaker drivers designed to produce high-frequency sounds (i.e., approximately 2 kHz-20 kHz). In these speaker systems, the woofers, midranges, and tweeters may each be housed in individual speaker housings. Separating the speaker drivers into individual speaker housings, however, can be detrimental to the uniformity and quality of sound received at a given location due to the different positions of the individual speakers. For example, muddy sound localization and poor dialog intelligibility can also result due to the smearing of sound across multiple speakers. In addition, two or more sound sources spaced apart from each other and playing at the same frequency can cause a phenomenon called lobing to occur. Lobing occurs when the sound waves from two or more sound sources cancel each other out at some off-axis locations and reinforce at others, resulting in the degradation of the sound at some off-axis listening positions.
Other speaker systems include multiple speaker drivers in a single speaker housing. In these systems, the speaker drivers can be coupled to horn structures and/or waveguides positioned adjacent to each other within the single speaker housing. This configuration with the speaker drivers positioned near each other can provide a combined sound at a given location having better uniformity than in the speaker systems having speaker drivers in different housings. The speaker drivers, however, are still separated from each other and the separation can lead to a sub-optimal wave summation of the sounds emitted by the individual drivers, which may provide a non-coherent wave front at the device output.
Acoustic waveguides have been developed to provide improved sound distribution from selected drivers. Examples of such improved waveguides include the waveguides and associated technology set forth in U.S. Pat. Nos. 7,177,437, 7,953,238, 8,718,310, 8,824,717, and 9,204,212, each of which is incorporated herein in its entirety by reference thereto. These waveguides are configured to work with a single high frequency driver and are therefore limited in their operating bandwidth. It would be desirable to provide a waveguide that emits across an extended frequency range using one or more high-frequency drivers and one or more midrange drivers. The inventors of the present technology, however, have discovered substantive improvements to the conventional waveguide technologies to provide these and other benefits.